In a conventional disk array system, a structure having multiplexed DKCs and multiplexed power source units for supplying power source thereto is adopted for securing reliability. For example, a structure may be made so that a DKC is multiplexed, i.e., made into logical clusters (for example, CL1 and CL2), and 2 systems of power source units (for example, PS1 and PS2) are arranged to correspond thereto. From the PS1 and PS2, DC power sources (for example, DC1 and DC2) are supplied respectively to the clusters CL1 and CL2 of the DKC. In the above multiplexed structure example, even when one DC power source supply is suspended owing to a power failure or the like, the DKC is continuously operated by use of the other DC power source supply. Further, in the case where a battery is arranged to each of the power source units, even when the DC power source supply is stopped, the DKC is continuously operated by battery backup function. When both the DC power source supplies are stopped, both the clusters stop their operation. When the DC power source supplies are restarted at power recovery, by intervention of maintenance workers' operation, recovery processing by the clusters of the DKC is carried out, thereafter the DKC operation is restarted.
In Japanese Patent Application Laid-Open Publication No. 9-325836, an example of technologies for recover is described. It is described that, in this technology, control output is so made that devices to be power recovery objectives are recovered to their conditions before power failure, according to the power failure and recovery conditions of power sources, and device conditions before power failure are used as information for device recovery.